The present invention relates to a plug pin for an internal combustion engine fuel injector nozzle.
In known injectors, the nozzle is normally defined by a body having a conical wall with a number of fuel injection orifices; and the pin has a conical tip which closes the orifices by virtue of an axial force normally resulting from the force of a spring and the difference in fuel pressure on the pin and a control rod.
The conical tip of known pins is connected to a cylindrical portion of the pin by a truncated-cone-shaped portion, the outer surface of which forms, with the outer surface of the conical tip, an annular edge engaging a circumference of the nozzle wall to close the orifices and which is obviously subject to wear.
A drawback of known pins of the above type is that wear on the edge contacting the nozzle wall also shifts the contact circumference on the wall, thus also altering the closed position of the pin and consequently the travel or lift of the pin between the closed and open positions.
Moreover, the contact circumference gradually increases in diameter, so that, for a given opening travel of the pin, the amount of fuel injected also varies alongside wear. Consequently, the amount of fuel injected by the various injectors on the engine differs according to the different degrees of wear on the edges of the respective pins.
It is an object of the invention to provide a plug pin for an injector nozzle, which is extremely straightforward and cheap to produce, while at the same time ensuring constant fuel injection for a given lift of the pin to eliminate the aforementioned drawbacks typically associated with known pins.
According to the present invention, there is provided a plug pin for an internal combustion engine fuel injector nozzle, wherein said nozzle has a conical wall with orifices for injecting fuel, and wherein said pin comprises a tip for closing said orifices; an axial force acting on said pin to cause said tip to engage said wall at a portion adjacent to said orifices; and the pin being characterized in that said tip comprises a truncated-cone-shaped portion having an outer surface resting entirely on said wall.